Color filter

Abstract: A color filter having the thickness of 3 µm or smaller and, on a substrate, having color filter elements which have different colors each other and are made from a resist compositions comprising an alkali soluble resin and dyes having a specific color within the wave length range from 400nm to 700nm, wherein each of the color filter elements has the minimum light transmittance of 25% or smaller, and the color filter is excellent in various properties such as resolution, color tone, color reproductivity and color depth and it has a small thickness.

Description: This invention relates to a color filter which is used e.g. for producing a solid state camera element or a gas sensor. Color filters have been used in e.g. CCD and LCD. The color filters were usually dyed by a combination of three dyes of the three primary colors or of the three complementary colors. As the production method for the color filters, e.g. dyeing methods, electrodeposition methods, printing methods and resist methods have been used. However, dyeing a filter made of gelatin often causes problems such as uneven dyeing, swelling of materials or cracking. Electrodeposition methods and printing methods also have such a problem that a thick color filter is required in order to obtain a deep colored color filter. According to the resist methods, a deep colored color filter cannot be obtained. Thus all of the methods above mentioned have some problems. The object of this invention is to solve the above-mentioned problems and to provides a color filter which is excellent in various properties such as resolution, color tone, color reproductivity, and color depth. The subject matter of this invention is a color filter having a thickness of 3 µm or smaller and, on a substrate, having two or more kinds of color filter elements which have different colors, wherein the color filter element is made from a resist composition comprising an alkali soluble resin and dyes having a specific color within the wave length range from 400nm to 700nm and each of the color filter elements has a minimum light transmittance of 25% or smaller. Preferred color filters have a thickness of 2 µm or smaller and a minimum light transmittance of 20% or smaller. The color filter having a thickness of 1 µm or smaller is more preferable. The light transmittance can be obtained, for example, by measuring light transmittance of each of color filter elements formed on a quartz glass by a spectrophotometer. Though the method for producing is not critical, the color filter of this invention is usually produced by a resist method. Preferable color filters can be produced according to the following process a)-d). a) A resist composition comprising an alkali soluble resin, an organic solvent and a dye having a specific color within the wave length range from 400nm to 700nm is coated and dryed to form a coated film. b) Specific parts of the coated film thus formed are exposed to irradiation. c) The resulting coated film is developed by an alkaline developer to form a resist pattern i.e. a color filter element. d) a) to c) are repeated for different colors i.e. by using a dye having a different color from the dye used in a) within the wave length range from 400nm to 700nm. The resist composition used in above-mentioned process is prepared by filtering a composition comprising an alkali soluble resin, an organic solvent and a dye through a filter. The pore size of the filter is preferably 0.2 µm or smaller and more preferably 0.1 µm or smaller. An preferable color filter of this invention is that having color filter elements hardened by a crosslinking reaction. In order to produce said preferable color filter, a resist composition further comprising a crosslinking agent having a group represented by the following formula -(CH 2 ) s -OR 0 wherein R 0 represents a hydrogen atom or a lower alkyl group and s represents an integer from 1 to 4, is used in addition to the alkali soluble resin, the organic solvent and the dye. As an example of the alkali soluble resin, a novolac resin, a polyimide precursor, a copolymer of a vinylphenol such as a copolymer of styrene and maleic anhydride, a copolymer of styrene and vinylphenol, a copolymer of p-hydroxystyrene and p-acetoxymethylstyrene or polyvinylphenol can be mentioned. Examples of the novolac resin include a novolac resin used as an ingredient in a positive resist composition for the production of a semiconductor, such as a known novolac resin prepared by a condensation reaction between phenols and aldehydes in the presence of an acidic catalyst. Any phenols having been used for preparing the known novolac resins can be used for preparing the novolac resin in this invention. Examples of the phenols include phenol, cresol, ethylphenol, butylphenol, xylenol, phenylphenol, catechol, resorcinol, pyrogallol, naphthol, bisphenol C and bisphenol A. These phenols can be used either independently or in combination of two or more. As an example of the aldehydes, an aliphatic aldehyde or an aromatic aldehyde such as formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde and benzaldehyde can be mentioned. In order to modify the molecular distribution of the alkali soluble resin such as novolac resin to a preferable one, a mean such as a fractionation of the alkali soluble resin or adding a polyphenol, such as bisphenol C or bisphenol A to the alkali soluble resin may be conducted. Examples of the organic solvent include dioxane, methylcellosolve, ethylcellosolve, methylcellosolve acetate, ethylcellosolve acetate, diethyleneglycol dimethylether, ethyleneglycol monoisopropylether, propyleneglycol monomethylether, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, γ-butyrolactone, methylethylketone, methylisobutylketone, cyclopentanone, cyclohexanone, ethyl acetate, n-butyl acetate, propyleneglycol monomethylether acetate, propyleneglycol monoethylether acetate, methyllactate, ethylpyruvate and dimethylsulfoxide. These solvents can be used either independently or in combination of two or more. Either a positive resist composition or a negative resist composition can be used for producing the color filter of this invention. The positive resist composition comprises a quinonediazide compound as a dissolution inhibitor and the negative resist composition comprises a photo-induced acid precursor and crosslinking agent in addition to the alkali soluble resin, the organic solvent and the dye. Exposure of a coated film made from a positive resist to irradiation causes a solubility difference between exposed parts and unexposed parts, because the quinonediazide compound exposed to the irradiation decomposes and provides a compound soluble in an alkaline developer whereas the unexposed quinonediazide compound acts to lower the solubility of the alkali soluble resin to the alkaline developer. Exposed parts are removed by alkaline developer and unexposed parts remain to form a positive tipe resist pattern . The crosslinking agent acts to harden the positive resist pattern when it is heated. The photo-induced acid precursor decomposes to yield an acid when the positive resist pattern is exposed to irradiation and acts to harden the patterns. Exposure of a coated film made of a negative resist to irradiation makes the alkali soluble resin hardened due to the crosslinking agent and an acid yielded from the photo-induced acid precursor by the exposure to the irradiation. The unexposed parts comprising unhardened resin are removed by the alkaline developer and the exposed parts comprising hardened resin, which is insoluble in the alkaline developer remain to form negative tipe resist patterns. Examples of the quinonediazide compound include o-benzoquinonediazide sulfonic acid ester, o-benzoquinonediazide sulfonic acid amide, o-naphthoquinonediazide-4-sulfonic acid ester, o-naphthoquinonediazide-4-sulfonic acid amide, o-naphthoquinonediazide-5-sulfonic acid ester and o-naphthoquinonediazide-5-sulfonic acid amide. These esters and amides are known compounds and have been used, for example, in positive resist compositions used for producing semiconductors. Examples of the crosslinking agent having a group represented by the formula -(CH 2 ) s -OR 0 wherein R 0 and s are as defined above, include a compound represented by the following formula wherein Z represents -NR 1 'R 2 ' or phenyl, R 1 '-R 6 ' each independently represents a hydrogen atom, -(CH 2 ) s OH or -(CH 2 ) s OR 0 provided that at least one of the R 1 '-R 6 ' is -(CH 2 ) s OH or -(CH 2 ) s OR 0 , R 0 represents a lower alkyl group and s represents an integer from 1 to 4 and compounds represented by the following formulae As the example of the preferable crosslinking agent, hexamethylether, hexaethylether and hexapropylether of hexamethylolmelamine can be mentioned. Any photo-induced acid precursor can be used as long as it can yield an acid directly or indirectly by an exposure to an irradiation such as ultraviolet, far ultraviolet, electron beam and X ray. Example of the photo-induced acid precursor include trihalomethyltriazine compounds mentioned in JP-A-92-163552; disulfone compounds mentioned in JP-A-89-57777; a compound represented by the following compound Z 8 -SO 2 -SO 2 -Z 9 -SO 2 -SO 2 -Z 10 wherein Z 8 and Z 10 each independently represents an aryl, aralkyl, alkyl, cycloalkyl or heterocyclic group which may be substituted and Z 9 represents an aryl group which may be substituted; a photo-induced acid precursor having a sulfonic acid ester group mentioned in JP-A-89-293339; a compound represented by the following compound CF 3 -SO 2 -O-(CH 2 ) p -Z 11 wherein Z 11 represents an aryl group which may be substituted and p represents 0 or 1; a compound represented by the following compound CF 3 -SO 2 -O-[C(Z 12 )(Z 13 )] q -C(O)-Z 14 wherein Z 12 and Z 13 each independently represents an alkyl, alkoxy or aryl group which may be substituted, Z 14 represents an aryl group which may be substituted and q represent 1 or 2; a compound represented by the following compound CF 3 -SO 2 -O-N(Z 15 )-C(O)-Z 16 wherein Z 15 represents an alkyl group which may be substituted and Z 16 represents an aryl group which may be substituted; and a compound represented by the following compound CF 3 -SO 2 -O-N=C(Z 17 )(Z 18 ) wherein Z 17 represents a hydrogen atom, an alkyl or aryl group which may be substituted and Z 18 represents an aryl group which may be substituted. As the more concrete example of the photo-induced acid precursor, a triazine compound represented by the following formula wherein Y 3 -Y 5 each independently represents an alkyl, alkenyl, aryl, aralkyl or piperidino group which may be substituted, -N(Y 6 )(Y 7 ), -OY 8 or -SY 9 provided that at least one of Y 3 -Y 5 represents mono-, di- or trihalogen substituted alkyl and Y 6 - Y 9 each independently represents a hydrogen atom, an alkyl or aryl group which may be substituted; an acetophenone derivative represented by the following formula wherein Y 1 and Y 2 each independently represents a hydrogen atom or a lower alkyl group; a disulfone compound represented by the following formula wherein A 1 and A 2 each independently represents a hydrogen atom, a halogen atom, a lower alkyl group or a lower alkoxy group; sulfonic acid derivatives represented by the following formulae and and onium salts represented by the following formulae can be mentioned. As the dye having a specific color in the wave length range from 400nm to 700nm, a dye having one of the three primary colors or one of the three complementary colors and being soluble in an organic solvent as well as an alkaline developer can be preferably mentioned. The dyes are dyes having a color of cyan, magenta, yellow, red, blue or green and also having a sulfonamide group substituted by one substituent. As examples of the dyes, coumarin styryl, azo, anthraquinone, xanthenium and phthalocyanine dyes can be mentioned. As a preferable example of the yellow dye, a dye represented by the following formula (I) B-A-M wherein M represents a group represented by the following formula wherein R 1 -R 3 each independently represents a hydrogen atom, a halogen atom, -SO 3 M' or -SO 2 -NH-R provided that at least one of R 1 -R 3 is -SO 2 -NH-R, M' represents an alkali metal atom, a quarternary alkyl ammonium salt or preferably a hydrogen atom and R represents an alkyl cyclohexylalkyl, alkylcarbonylaminoalkyl, alkoxy, alkoxyalkyl, aryl, aralkyl or cyclohexylalkyl group, which may be substituted; A represents a linking group represented by one of the following formulae and wherein R 4 -R 12 each independently represents a hydrogen atom, a halogen atom, a methyl group, -SO 3 M' or -SO 2 -NH-R (M' is as defined above); and B is M or a group represented by one of the following formulae and can be mentioned. As a preferable example of the magenta dye, a dye represented by the following formula (II) wherein R 13 -R 16 each independently represents a hydrogen atom, an alkyl or aryl group which may be substituted, R 17 -R 19 each independently represents a hydrogen atom, an alkyl group, an aryl group, -SO 3 M' or -SO 2 -NH-R provided that at least one of R 17 -R 19 is -SO 2 -NH-R and M' and R are as defined above, can be mentioned. As a preferable example of the cyan dye, a dye represented by the following formula (III) wherein Pc represents a phthalocyanine nucleus , h and i each independently represents a mean substitution number of -SO 3 M' and -SO 2 -NH-R respectively, M' and R are as defined above provided that h+i≦4, h≦3 and 1≦i≦4, can be mentioned. Examples of the dye represented by the formula (I) include a dye represented by one of the following formulae: and wherein X, Y and Z' each independently represents -SO 3 M' or -SO 2 -NH-R provided that at least one of X, Y and Z' is -SO 2 -NH-R and M' and R are as defined above, and the like. Examples of the dye represented by the formula (II) include a dye represented by one of the following formulae: and wherein X, Y and Z' each independently represents -SO 3 M' or -SO 2 -NH-R provided that at least one of X, Y and Z' is -SO 2 -NH-R and M' and R are as defined above. The dye used in this invention can be obtained, for example, by chlorinating a dye having a sulfonic acid group according to a usual manner to obtain a sulfochloride and reacting the sulfochloride thus obtained with a primary amine. The dye used in this invention can also be obtained by chlorinating a precursor of the dye to obtain a sulfochloride, reacting the sulfochloride thus obtained with a primary amine and then altering the resulting compound to the aimed dye. Examples of the dye having a sulfonic acid group include dyes selected from C.I. Acid Color or Direct Color in Color Index, etc. The amount of the dye in the positive resist composition is usually from 1 to 300 parts by weight, preferably 100 to 300 parts by weight, based on 100 parts of the quinondiazide compound. When the alkali soluble resin contains a novolac resin, the preferable amount of the alkali soluble resin is 1.5 parts by weight or less based on 1 part by weight of the dye. The preferable amounts of the crosslinking agent and the photo-induced acid precursor vary according to the situation where they are used. The color filter of this invention is excellent in various properties such as resolution, color tone, color reproductivity and color depth and it has a small thickness. Next, this invention will be explained in more detail with reference to the following examples. In the examples, "parts" represents "parts by weight" unless otherwise referred to. Referential example 1 A mixture of 20g of an acidic dye represented by the following formula (Suminol Milling Yellow MR, manufactured by Sumitomo Chemical Co., Ltd.), 100 ml of thionyl chloride and 15g of dimethylformamide was allowed to react for 30 minutes under refluxing and the resulting mixture was poured into iced water, then extracted with organic solvent, washed with water, dried and concentrated to obtain the sulfonylchloride compound. The sulfonylchloride compound thus obtained was reacted with 3-(2-ethylhexyloxy)propylamine with the molar ratio of 1 : 2 in tetrahydrofuran to obtain the sulfonamide compound. Referential example 2 According to the same manner as in Referential example 1 except that a dye represented by the following formula was used, the sulfonylchloride compound was obtained. The sulfonylchloride compound thus obtained was reacted with 3-(2-ethylhexyloxy)propylamine with the molar ratio of 1 : 1 in tetrahydrofuran to obtain the sulfonamide compound. Referential example 3 0.2 Part of hexaethoxymethylolmelamine, 1 part of cresol novolac resin produced by reacting m-cresol, p-cresol and formalin with the molar ratio of 5 : 5 : 7.5, 0.7 part of o-naphthoquinonediazide-5-sulfonicacidester (wherein two hydroxy groups were esterified in average) of a phenol compound represented by the following formula, 1.0 part of the sulfonamide compound obtained in Referential example 1, 3 parts of dimethylformamide and 6 parts of ethyllactate were mixed and the resulting mixture was filtered under an elevated pressure through a membrane filter having a pore size of 0.2 µm to prepare a positive resist composition. Referential example 4 Referential example 3 was repeated except that the sulfonamide compound obtained in Referential example 2 was used instead of the sulfonamide compound used in Referential example 3 to prepare a positive resist composition. Referential example 5 Referential example 3 was repeated except that Oleosol fast blue RL (a sulfonamide compound having copper-phthalocyanine nuclear, manufactured by Taoka Chemical Co.) was used instead of the sulfonamide compound used in Referential example 3 to prepare a positive resist composition. In the following examples, experiments were conducted according to the following condition unless otherwise referred to. As the substrate, CCD coated with acrylic resin was used. A resist composition comprising a dye, an alkali soluble resin, an organic solvent, etc. was coated on the substrate by mean of a spinner to form a resist film and the film was heated to remove the solvent. Then the resist film was exposed to irradiation through a patterned mask. When a negative resist was used, if necessary, the exposed resist film was heated at 180°C for 20minutes. Then the resist film was developed to obtain band type pattern or mosaic pattern. When a positive resist was used, the pattern thus obtained was exposed to irradiation and heated at 180°C for 20 minutes to prepare a color filter. The exposure to a ray was conducted with HITACHI LD-5010-i (NA=0.40, an I-line Stepper manufactured by Hitachi Ltd.) or NIKON NSR (NA=0.50, an I-line Stepper manufactured by Nikon Corp.). As the developer, SOPD (manufactured by Sumitomo Chemical Co.) or 3% aqueous solution of tetramethylammonium hydroxide was used. Example 1 Using each of the resist composition prepared in Referential example 3, 4 and 5 successively, above-mentioned process was conducted three times to obtain a color filter. The color filter thus obtained is excellent in various properties such as resolution, color tone, color reproductivity and color depth and has 1 µm. a thickness of not more than In each of the wave length ranges of the three dyes, the minimum light transmittance was not more than 25 %. Referential example 6 Referential example 3 was repeated except that the sulfonamide compound represented by the following formula wherein R' is -SO 2 NH(CH 2 ) 3 O(CH 2 ) 7 CH 3 and R'' is H or R', was used instead of the sulfonamide compound used in Referential example 3 to prepare a positive resist composition. Referential example 7 Referential example 3 was repeated except that the sulfonamide compound represented by the following formula wherein R''' is -SO 2 NH(CH 2 ) 3 O(CH 2 ) 7 CH 3 , was used instead of the sulfonamide compound used in Referential example 3 to prepare a positive resist composition. Example 2 Example 1 was repeated except that the resist composition prepared in Referential example 6, 7 and 5 were used successively to obtain a color filter. The color filter thus obtained is excellent in various properties such as resolution, color tone, color reproductivity and color depth and has a thickness of not more than 1 µm. In each of the wavelength ranges of the three dyes, the minimum light transmittance was not more than 25 %. Referential example 8 Referential example 1 was repeated except that 1,5-dimethyl-heptylamine was used instead of 3-(2-ethylhexyloxy)propylamine to obtain a sulfonamide compound. Referential example 9 0.3 Part of hexaethoxymethylolmelamine, 1 part of cresol novolac resin produced by reacting m-cresol, p-cresol and formalin with the molar ratio of 5 : 5 : 7.5, 0.7 part of o-naphthoquinonediazide-5-sulfonicacidester (wherein two hydroxy groups were esterified in average) of a phenol compound represented by the following formula, 0.7 part of the sulfonamide compound obtained in Referential example 8 and 9.5 parts of ethyllactate were mixed and filtered under an elevated pressure through a membrane filter having a pore size of 0.2 µm to prepare a positive resist composition. Referential example 10 Referential example 9 was repeated except that a mixture of 0.3 part of a novolac resin produced by reacting a compound represented by the following formula and formalin with the molar ratio of 0.95 : 1 and 0.7 part of MARUCALINCUR-CST-70 (stylene-vinylphenol copolymer, manufactured by Maruzen Oil Co. Ltd.) instead of 1 part of the cresol novolac resin used in Referential Example 3 to prepare a positive resist composition. Example 3 Example 1 was repeated except that the resist composition prepared in Referential example 9, 4 and 5 were used successively to obtain a color filter. The color filter thus obtained is excellent in various properties such as resolution, color tone, color reproductivity and color depth and has a thickness of not more than 1 µm. In each of the wavelength ranges of the three dyes, the minimum light transmittance was not more than 25 %. Example 4 Example 1 was repeated except that the resist composition prepared in Referential example 10, 4 and 5 were used successively to obtain a color filter. The color filter thus obtained is excellent in various properties such as resolution, color tone, color reproductivity and color depth and has a thickness of not more than 1 µm. In each of the wave length ranges of the three dyes, the minimum light transmittance was not more than 25 %. Referential example 11 Referential example 10 was repeated except that 0.2 part of a photo-induced acid precursor represented by the following formula was used instead of 0.7 part of o-naphthoquinonediazide-5-sulfonicacidester and a mixed solvent of 3.5 parts of N,N-dimethylformamide and 6 parts of ethyllactate was used instead of 9.5 parts ethyllactate to prepare a negative resist composition. Referential example 12 Referential example 11 was repeated except that Oleosol fast blue RL (a sulfonamide compound having copper-phthalocyanine nuclear, manufactured by Taoka Chemical Co.) was used instead of the sulfonamide compound obtained in Referential example 6 to prepare a negative resist composition. Referential example 13 Referential example 11 was repeated except that the sulfonamide compound obtained in Referential example 2 was used instead of the sulfonamide compound obtained in Referential example 6 to prepare a negative resist composition. Example 5 Example 1 was repeated except that the resist composition prepared in Referential example 11, 12 and 13 were used successively to obtain a color filter. The color filter thus obtained is excellent in various properties such as resolution, color tone, color reproductivity and color depth and has a thickness of not more than 1 µm. In each of the wave length ranges of the three dyes, the minimum light transmittance was not more than 25 %.

Claims: A color filter having a thickness of 3 µm or smaller and, on a substrate, having two or more color filter elements which have different colors wherein each color filter element is made from a resist composition comprising an alkali soluble resin and dyes having at least one sulfonamide group substituted by one substituent and having a specific color within the wavelength range from 400 nm to 700 nm and each of the color filter elements has a minimum light transmittance of 25 % or smaller. The color filter according to claim 1 wherein the thickness of the color filter is 2 µm or smaller and the minimum light transmittance is 20% or smaller. The color filter according to claim 1 or 2 which is produced according to the following process a)-d); a) a resist composition comprising an alkali soluble resin, an organic solvent and a dye having a specific color within the wavelength range from 400nm to 700nm is coated on a substrate and dried to form a coated film, b) specific parts of the coated film thus formed are exposed to irradiation, c) the resulting coated film is developed by an alkaline developer to form a color filter element, and d) a) to c) are repeated by using a dye having a different color from the dye used in a) within the wave length range from 400nm to 700nm. The color filter according to claim 3 wherein the color filter elements are hardened by crosslinking reaction. The color filter according to claim 3 or 4 wherein the resist composition further comprises a crosslinking agent having a group represented by the following formula -(CH 2 ) s -OR 0 wherein R 0 represents a hydrogen atom or a lower alkyl group and s represents an integer from 1 to 4. The color filter according to any one of claims 1 to 5 wherein the dyes having a specific color within the wave length range from 400nm to 700nm are a dye represented by the following formula (I) B-A-M wherein M represents a group represented by the following formula wherein R 1 -R 3 each independently represents a hydrogen atom, a halogen atom, -SO 3 M' or -SO 2 -NH-R provided that at least one of R 1 -R 3 is -SO 2 -NH-R, M' represents an alkali metal atom, a quaternary alkyl ammonium salt or a hydrogen atom and R represents an alkyl, cyclohexylalkyl, alkylcarbonylaminoalkyl, alkoxy, alkoxyalkyl, aryl, aralkyl or cyclohexylalkyl group which may be substituted, A represents a linking group represented by one of the following formulae and wherein R 4 -R 12 each independently represents a hydrogen atom, a halogen atom, a methyl group, -SO 3 M' or -SO 2 -NH-R (M' is as defined above), and B is M or a group represented by one of the following formulae and a dye represented by the following formula wherein R 13 -R 16 each independently represents a hydrogen atom, an alkyl or aryl group which may be substituted, R 17 -R 19 each independently represents a hydrogen atom, an alkyl group, an aryl group, -SO 3 M' or -SO 2 -NH-R provided that at least one of R 17 -R 19 is -SO 2 -NH-R and M' and R are as defined above; and a dye represented by the following formula wherein Pc represents a phthalocyanine nucleus, h and i each independently represents a mean substitution number of -SO 3 M' and -SO 2 -NH-R respectively, M' and R are as defined above provided that h+i≦4, h≦3 and l≦i≦4. The color filter according to any one of claims 1 to 6 wherein the resist composition is a positive resist composition which further comprises a quinondiazide compound. The color filter according to claim 7 wherein the positive resist composition further comprises a crosslinking agent. The color filter according to claim 7 or 8 wherein the positive resist composition further comprising a photo-induced acid precursor. The color filter according to any one of claims 1 to 6 wherein the resist composition is a negative resist composition which further comprises a crosslinking agent and a photo-induced acid precursor. The color filter according to claim 8 wherein the weight ratio of the dye to the quinondiazide compound is 1: 1 or more. The color filter according to claim 11 wherein the alkali soluble resin in the resist composition contains a novolac resin and the weight ratio of the alkali soluble resin to the dye is 1.5 : 1 or less.

Inventors: HISHIRO YOSHIKI, TAKEYAMA NAOKI, YAMAMOTO SHIGEKI, HISHIRO, YOSHIKI, TAKEYAMA, NAOKI, YAMAMOTO, SHIGEKI
Applicants: SUMITOMO CHEMICAL CO, SUMITOMO CHEMICAL COMPANY LIMITED
Application year: 1994
Main classification: G03C7
IPC codes: G03F7, G02B5